1. Field of the Invention
The present invention relates to power driven conveyors and, more particularly, to apparatus having a power driven conveyer section feeding to a gravity section feeding, in turn, to another power driven conveyer section.
2. Description of Related Art
In the commercial baking industry, the use of conveyors for the movement of tortillas is generally well known. The term "conveyor" is intended to mean any apparatus suitable for moving objects from one point to another without manual labor, including, but not limited to, an endless belt conveyor driven around two axles, one powered, or drive, axle and one non-powered, or idler, axle. The term "tortilla" as used herein is intended to refer to a piece of dough having a generally disked or other similar shape. However, while the invention is intended for use with disk shaped dough pieces, it may work with objects having other shapes, such as cakes, torts, rolls, or cookies.
Two types of apparatus which commonly utilize conveyors are ovens for the baking of food products and cooling racks for the cooling of freshly baked food products. Due to space constraints, the horizontal conveyors within these ovens and cooling racks are usually arranged in a vertically stacked, or tiered, relationship. The tortillas generally enter the tier at the top and move, in a serpentine fashion, through the tier and exit at the bottom. The horizontal component of the serpentine movement is provided by the conveyors, while the downward vertical movement is provided by a transfer guide mounted at the end of each conveyor. To facilitate the horizontal component of the serpentine movement, the upper surface of the conveyor mounted on each level of the tier moves in the opposite direction to the upper surfaces of the conveyors mounted above and below, so that the tortillas move back and forth across the length of the tier as they travel from its entrance to its exit. Each transfer guide guides the tortillas through a generally downward semicircular path to the upper surface of the next conveyor.
Generally, such automated apparatus is quite expensive, thus the production of large quantities of product is necessary to bring the per-unit cost down to a competitive level. A common method used to increase production is to widen the conveyors and to increase their velocity, so that more product can be carried at a higher speed.
An oven having a tier of endless belt conveyors is provided for in Eagerman U.S. Pat. No. 2,709,412. In this oven, the tier of parallel conveyors moves bagels, or other similarly shaped dough pieces, through the oven at a speed sufficient to allow proper baking. A semicylindrical transfer guide is provided for at the end of each conveyor so that the bagels are guided from one conveyor to the next, in sequence. To assure even baking, the transfer guide also turns the bagels over as they travel to the next lower conveyor.
The inventors have no reason to believe that the transfer guide described in the Eagerman patent is not generally effective in guiding tortillas from an upper conveyor to a lower conveyor. However, when prior art devices of that general configuration are operated under conditions intended to increase the rate of production, certain difficulties may be encountered. As described above, it is generally desirable to produce large quantities of product to hold the per-unit cost down to a competitive level. Accordingly, it is often desirable to have tiered conveyors capable of increased velocities and also wide enough to accommodate several laterally spaced rows of tortillas. One drawback of the transfer guides designed according to the prior art is the failure of the guide to correct the position of laterally misaligned tortillas.
Another drawback of the prior art transfer guides is that dough entering the guide at a high velocity may inadvertently move laterally. More particularly, when a tortilla travels at a high velocity through a downward, semi-circular turn, a variety of factors may interact to cause unwanted lateral movement. Thus, it is possible for a once properly aligned tortilla to move laterally while it is on the transfer guide. While the applicants do not precisely understand all the associated causes of the unwanted lateral movement, one cause may be unwanted acceleration forces created by high velocity circular turn. Further causes may be attributable to the vibration of or the bouncing of the tortilla against the transfer guide. Also, air resistance may induce the unwanted lateral movement through lift or drag effects.
This unwanted lateral movement may cause some of the dough to fly off of the guide and out of the tier, resulting in waste. Moreover, the unwanted lateral movement can also destroy the lateral separation between adjacent pieces of dough, resulting in undesirable bunching which may disrupt subsequent automated processes, such as stacking and packaging. Furthermore, in applications where dough pieces having large, flat surface areas, such as tortillas, must be processed, the loss of the lateral separation may result in undesirable overlapping, which could disrupt even baking or cooling.
It should, therefore, be appreciated that there still is a need for a transfer guide that successfully guides laterally spaced rows of tortillas between two conveyors so that the tortillas exit onto the lower conveyor with the proper lateral spacing. Accordingly, the present invention fulfills this need.